Digital image processing devices, such as digital cameras, use automatic white balancing (AWB) in order to provide accurate colors for pictures reproduced from captured images. AWB is a process that finds or defines the color white in a picture called the white point. The other colors in the picture are determined relative to the white point. The AWB adjusts the gains of different color components (for example, red, green, and blue) with respect to each other in order to present white objects as white, despite the color temperature differences of the image scenes or different sensitivities of the color components. When the white point is incorrect, however, the reproduced image may include erroneous colors. These color errors may occur because of manufacturing variances among cameras, whether in the hardware or software, which can cause variations in chromaticity response or color shading. Also, residual shading issues may exist that introduce false colors into the image. This may occur due to difficult lighting (illumination) situations such as a mix of daylight and other human-manufactured light sources for example. The AWB module may then use the false colors in its calculations leading to even further degradation of the reproduced image. Otherwise, uni-colored images, when no clear white point exists in the image, also tend to be difficult for AWB algorithms to process leading to erroneous colors.
One type of color error caused by an erroneous white point is called a color cast where an entire image, parts of an image, or certain objects within the image have the same incorrect shade. For human faces or skin, even slight errors in skin color or skin tone can be easily detected by the average person viewing the image. Thus, when color cast exists on a human face or other areas of skin in a picture, the face or skin may seem too purple, blue, red, green, pink, grey, or yellow for example.